Understanding the Universe: Galaxies, Constellations, and Stars

1. Do Now!You have until • List the following words in order from smallest to largest: Constellation Planet Solar System Star Universe Galaxy • How many of the smaller word can fit into the next word on your list? Example: If you thought stars were smaller than a solar system you can say there are 1000 stars in a Solar System.

2. “Galaxies” • A. Galaxies are very large groups of stars. • B. Most contain 100s of billions of stars! • C. They are classified by shape. • 1. Spiral: a) “Nucleus with Arms” b) The center is full of many yellow stars, which makes it look like a nucleus. c) Many spiral arms come out of the nucleus.

3. a) Spherical, without spiral arms. • 2. Elliptical: b) The oldest stars are in this type of galaxy. c) No new star activity. • 3. Irregular: a) Does not have a definite shape. b) Could be the result of two galaxies colliding. c) The Megallanic Clouds are an example of a irregular galaxy.

4. III. Our Galaxy: “The Milky Way” • A. Spiral shaped • B. 100,000 light years across. • C. Our solar system is located in one of the spirals, 30,000 light years from the nucleus.

5. E. The closest star in our galaxy, besides the sun, is Proximi Centauri. (About 4 light years away.) Alpha and Proximi Centauri

6. IV. How the Terms Fit Together: • A. A star and its planets = A solar system! • B. A group of stars = A constellation! • C. Billions of stars = A galaxy! • D. Several galaxies = A Cluster!

7. 2. The other galaxies in the local group are : • 1. The cluster that the Milky Way is located in is called the Local Group. • - Amdromeda ( Spiral) • - Megallanic Clouds IRREGULAR

8. “Constellations” • A. Constellations are groups of stars that appear to form some type of pattern in the sky. • B. Most of the time stars, in a particular constellation, do not have a relationship with each other. • C. Most constellations are named after Greek and Roman mythological figures. • D. Astronomers have divided the sky into 88 constellations. • E. Constellations give stars specific location in the sky. • Ex. 1. Polaris is in the handle of Ursa Minor. (Little Dipper) • Ex. 2. Betelgeuse is in the right shoulder of Orion.

9. BETELGUESE

10. Why are Constellations Useful? • A. Used as landmarks to locate other objects in space. • B. Were used by sailors and explores as a navigational tool. C. USED FOR ENTERTAINMENT D. USED TO KEEP TRACK OF TIME/SEASONS FOR TASKS • Seasonal Changes: • A. Different constellations can be seen at different times of the year.. • i. Due to the Earth’s revolution around the Sun. • Ii. Ex. Orion can be seen in the winter and spring . Pegasus can only be seen in summer and fall.

11. What is your Sign? • A. Aries- (March 21-April 19) • B. Taurus- (April 20 - May 20) • C. Gemini- (May 21 - June 20) • D. Cancer- (June 21 - July 22) • E. Leo- (July 23 - August 22) • F. Virgo- (August 23 – September 22)

12. (September 23 - October 22) • H. Scorpius- (October 23 - November 21) • G. Libra- • I. Sagittarius- (November 22 - December 21) • J. Capricornus- (December 22 - January 19) • K. Aquarius- (January 20 - February 18) • L. Pisces- (February 19 - March 20) www.astro.wisc.edu/.../ extra/constellations.html

13. Circumpolar constellations • B. Some Constellations can be seen all year long! • These type of constellations are called circumpolar. • Ex. Of circumpolar constellations are Ursa Major & Ursa Minor (Big & Little Dipper).

14. “The Life of Stars” I. Intro. to Stars: A. Star- hot, bright, sphere of gas. B. Stars are classified by their luminosity. 1. Luminosity- How bright a star is. C. There are many things that can affect stars luminosity. Distance Optics Size Stage of Life Temperature

15. D. Types of Magnitude: 1. Apparent Magnitude- The luminosity of a star as we see it from earth. • Apparent Magnitude tells you very little about a star. 2. Absolute Magnitude- The measure of a star’s actual luminosity. a.) A formula is used to figure absolute magnitude out. b.) A chart of the brightest stars is then made. c.) This chart shows how luminous each star would look if they were all the same distance from Earth.

16. E. Star Color: 1. Color – Can indicate the estimated temperature of a star. a.) Red- (Coolest star) 3000-4000 K b.) Yellow- (The Sun) 4000-7000 K c.) White- 7000-11,000 K d.) Blue- (Hottest Star) 11,000-60,000 K

18. II Life Cycle of Stars: A. Stars are born in nebulas. B. Nebula- A rapidly condensing cloud of gas and dust. C. Star “Pre-life Steps” 1. Gases rapidly condense to star dust. 2. Masses form 3. Masses collide with others to form larger pieces of “star stuff”. 4. Gravitational forces increase.

19. 5. This sets off a “snow ball effect” or chain reaction. 6. One very large object collects most of the “star stuff”. 7. Density increases. 8. Temperature increases. 9. Fusion begins to take place. a.) Fusion- The process in which two atoms fuse together to form another substance. b.) In the suns case there were two atoms of Hydrogen, which fused together to form Helium. 10.When fusion out put becomes balanced with the gravity of the large object, a star is born.

20. 1. Main Sequence- The beginning phase of life for all stars. • D. Life Cycle Steps: a.) Every Star has a main sequence. b.) The star spends most of its life in this phase. c.) Fusion continues for billions of years. d.) When a star’s hydrogen begins to run out, the star begins to enter its next phase. e.) It can go in one of two directions depending on size: * Red Giant Phase (Small & Medium stars) * Super Giant Phase (Large & Extra Large stars)

21. E. Small & Medium Stars: (low mass stars) 2. Red Giant Phase- Beginning stage of death for small & medium size stars. a.) The fusion and gravity of a star becomes unbalanced do to hydrogen running out. b.) This makes the star collapse in on it self. c.) Another round of fusion is triggered. This time helium fusses together. d.) The star swells to several times its original size f.) Remaining gas floats away as the star cools.

22. 3. White Dwarf- The remaining core of a small or medium star after the red giant phase is over. a.) The stars weight during the red giant phase will make the star collapse in on it-self. b.) All that is left of the star now is a collapsed core. c.) About the size of earth. 4. Black Dwarf- The final stage of death of a small or medium size star. a.) After the stars core cools enough that its luminosity is zero a star enters this phase of life. b.) All that is left is a tiny ball of “lifeless material”

23. F. Large & X-Large Stars: (high mass stars) 2. Super Giant Star Phase- A star enters this phase when most of the stars hydrogen is used up. a.) This causes a Super Nova. b.) Super Nova- A rapid expansion of the star that appears to be an explosion. c.) Gases eventually escape to form new nebulas.

24. 3. Neutron Star Phase- The remaining core after a super nova. a.) Very small and dense. (10-15 Km across) b.) Can be double its original density. 4. Pulsar Star Phase- A rapidly spinning neutron star. a.) It is spinning so fast that it looks like little pulses of light are coming off of it. b.) Total collapse of the star is near when it enters this phase.

25. 5. Black Hole Phase- This is the final stage of death for a large/x-large star. a.) A total collapse of the star’s core takes place. b.) A black hole is extremely dense and has a very high gravitational force. c.) Almost nothing can escape its gravitational pull. (not even light)